SAP R / 3 Sync project setup fails --> NOT_AUTHORIZED


We are currently preparing to go live with version 8.0.3.
We test all interfaces and in the case of the sync project for SAP R / 3 we came across a new error that has not yet occurred.

When setting up the SAP Sync project, we use the same service account as our current version 6 in production runs. The following error now occurs during verify connection settings within Synchronization Editor:

Error calling method TestCUA by method request. (Error [1777217] Error loading schema of schema type (SAP R/3 (System PUM, client 600 - CUA central system))!
[SAP.Middleware.Connector.RfcAbapException] NOT_AUTHORIZED)

Are there differences in the necessary authorizations between version 6.1.3 and version 8.0.x in order to set up a SAP synchronization?

Thanks for any piece of advice!

Kind Regards